Microwaves And How They Work - Panasonic NN-DS59NB Operating Instructions Manual

Microwaves and How They Work

Microwaves are a form of high frequency radio waves
similar to those used by a radio, including AM, FM
and CB. They are similar to a television where the
radio waves are converted to a picture on the screen.
However, microwaves are much shorter than radio
waves; approximately twelve centimetres wave length.
Electricity is converted into microwave energy by the
magnetron tube (which is the heart of the microwave
oven).
From the magnetron tube, microwave energy is
transmitted to the oven cavity. The microwaves are
converted to heat in the food. The microwaves enter
from the outside of the food and travel through the
food losing half of their power every two to three
centimetres. Continued cooking to the centre occurs
by conduction.
Although pacemakers used to be affected by
microwaves (as well as by other radio waves), they
are now shielded and are not bothered by these
interferences. This allows people with pacemakers
to sit calmly by their radio or television and cook with
microwave ovens.
When microwaves come in contact with a substance,
any one or combination of three things may occur.
They can be:
1. REFLECTED
2. TRANSMITTED
3. ABSORBED
Reflection
Metal substances REFLECT microwave energy and
because there is no absorption, there is no heating.
This is why the oven interior is either stainless steel or
epoxy-coated steel. This ensures that the microwaves
are kept inside the cavity and evenly distributed
throughout the food.
Transmission
Such substances as paper, glass and plastic
TRANSMIT microwave energy and do not become
hot except from food. Because these substances do
not reflect or absorb microwave energy, they are ideal
materials for microwave cooking containers.
Absorption
Food contains moisture and will ABSORB microwave
energy, which causes the moisture molecules within
the food to vibrate at an incredible rate (2,450,000,000
times per second). Friction, created by the vibration,
produces heat energy which is conducted throughout
the food.
It is important to use the correct container when
cooking in a microwave oven. The following will help
you make the right selection.
How to Test a Container for Safe
Microwave Oven Use
TO TEST A CONTAINER FOR SAFE MICROWAVE
OVEN USE: Fill a 1-cup glass measure with cool
water and place it in the microwave oven alongside
the empty container to be tested; heat one (1) minute
at 1000 W. If the container is microwave ovensafe
(transparent to microwave energy), the container
should remain comfortably cool, the water in glass
measure should be hot. If the container is hot, it has
absorbed some microwave energy and should NOT be
used. This test cannot be used for plastic containers.
Paper Products and Freezer Wrap
Waxed paper, paper plates, cups and napkins should
not be used for heating or cooking food. Freezer wrap
should not be used as it is not heat resistant and
may melt. Paper towel, greaseproof paper and bake
paper may be safely used for short periods of time for
covering or lining.
Glass, Ceramic and China
Heat-Resistant glass cookware is invaluable in
microwave cooking. Many of these items are readily
available in most homes: glass jugs, mixing bowls, loaf
dishes, covered casseroles, oblong baking dishes, pie
plates and round or square cake dishes. Examples of
this type of cookware are Pyrex and Corningware
®
Dinnerware can be used for microwave heating. Many
brands of dinnerware are microwave safe. Check
the care information for reference to microwave use
for dinnerware and serving pieces. If dinnerware
is marked ovenproof, it frequently is safe to use in
the microwave oven. However, to be sure, check by
conducting microwave dish test previously mentioned.
Several types of glassware and dinnerware are not
recommended for use in the microwave oven. Do not
use dishes with metallic trim or containers with metal
parts. Do not use cups or mugs with glued on handles,
as they may fall off with continued heating. Do not use
delicate glassware. Although the glassware may be
transparent to microwave energy the heat from the
food may cause the glassware to crack.
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Microwaves and How They Work
Plastic
Plastic dishes, cups and some freezer containers
should be used with care in a microwave oven. Choose
plastic containers carefully, as some plastic containers
may become soft, melt and may scorch. The majority
of plastic dishes, even those designed for use in the
microwave oven, are not suitable for cooking foods
with high fat or sugar content, or for lengthy cooking
times. Most microwave plastic dishes should not be
used for longer than 3 to 5 minutes on 1000 W. These
dishes, although not suitable for extended cooking,
may be used successfully for defrosting or for use on
lower power levels.
Cooking Bags designed to withstand boiling, freezing,
or conventional heating are microwave safe. Prepare
bags according to manufacturer's directions. When
cooking by microwave, DO NOT use wire twistties
to close bag. They can act as an antenna and cause
arcing (sparks).
DO NOT COOK IN PLASTIC FOOD STORAGE
BAGS. Cling Film such as GLAD WRAP
to cover dishes in most recipes. Over an extended
heating time, some disfiguration of the wrap may
occur. When removing cling film "covers", as well as
any glass lid, be careful to remove it away from you to
avoid steam burns.
Loosen plastic but let dish stand, covered.
Jars and Bottles
Jars and bottles can be used to warm food to serving
temperature, if the lid is removed first. Cooking should
not be done in these containers since most are not
.
®
heat resistant and during extended heating times, heat
from food would cause cracking or breaking.
Metal
Metal cookware or utensils, or those with metallic
trim, should NOT be used in the microwave. Since
microwave energy is reflected by metal, foods in
metal containers will not cook evenly. There is also a
possibility of "arcing".
Although metal utensils should be avoided in
microwave cooking, some metal can be helpful when
used correctly. Aluminum foil can be used safely, if
certain guidelines are followed, to prevent overcooking.
Small pieces of foil are used to shield areas such
as chicken wings, tips of roasts, or other thin parts
that cook before the rest of the recipe is finished.
Make sure foil is attached securely and doesn't touch
sides of oven, otherwise arcing may occur. Foil lined
containers, either cardboard or plastic, should NOT be
used in the microwave oven as arcing could occur.
Metal twist-ties, either paper or plastic coated, should
NOT be used in the microwave oven. Frozen dinner
trays can be used in the microwave, if the container
can be used is no deeper than 2 cm and is filled with food. Metal
®
skewers can not be used in microwave ovens as
arcing may occur. Wooden skewers are readily
available and give the same result.
Shells: Scalloped baking shells are best used during
reheating and for short periods of cooking time only.
Thermometers are available for use in microwave
ovens. DO NOT USE CONVENTIONAL MERCURY
TYPE CANDY OR MEAT THERMOMETERS in food
while cooking in the microwave oven.
Straw, Wicker and Wood
Straw and wicker baskets may be used in the
microwave oven for short periods of time to warm
rolls or bread. Large wooden utensils, such as bowls
or cutting boards should NOT be used for prolonged
heating as the microwave energy may cause the wood
to become dry and brittle.
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(continued)